No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 51 



plainly recognize a couple of fiber cones, though they were much 

 smaller than in the testes of Batrachoseps. These Triton testes 

 had been fixed in Flemming's chromo-osmic-acetic mixture. The 

 spindle cones, which Osterhout has described from the mitosis 

 of the pollen cells of Equisetum, are exceedingly interesting, as 

 they recall the fiber-cone structures in our present cells, even if 

 their nature and origin be found to be entirely different. In the 

 pollen cells the mitosis begins with spindle cones, while in the 

 testes of Batrachoseps the mitosis ends with fiber cones. 



Spindle Bridge and Mid-Body. 



The spindle bridge is, as is now fully known, the remains of 

 the central spindle. After this spindle has passed through the 

 nucleus its fibers begin to diminish in number, several fibers 

 apparently fusing into one. I judge that such is the case, be- 

 cause as the fibers decrease in number they increase in thick- 

 ness without getting much shorter. At this stage the fibers 

 also show a beaded structure in the same manner as the con- 

 tractile fibers, though not quite so pronounced. This beaded 

 structure is also found in the fibers of the fiber cones (Fig. 

 116), but not in any of the mantle fibers. 



The spindle bridge remains a long time after the cells have 

 otherwise separated, and in places we find not only one such 

 bridge in the same cell but two, both starting from the same 

 place but in different directions, and connecting several cells 

 with each other (Fig. 32). 



The object of the cell bridge is probably to prevent the cells 

 from moving too far apart, and the formation of the mid-body 

 is perhaps only a quick way to dispose of the cytoplasm of the 

 cell, until it can be properly absorbed in the regular way by the 

 spheres. 



I have in another place suggested that the contemporaneous 

 beginning of certain stages in the mitosis by all the cells in 

 the same pocket may be due to some influence exerted or 

 communicated by the spindle bridge. This body is the only 

 visible connection between one or more cells in the same 

 pocket. The spindle bridges are only found between cells 

 which simultaneously begin the same stage of mitosis. 



